Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$209.50	6.305%	$222.709	$222.71	$222.70	$222.70
Purchase #2	$164.27	5.646%	$173.5447	$173.54	$173.55	$173.50
Purchase #3	$108.99	13.452%	$123.6513	$123.65	$123.65	$123.70
Purchase #4	$129.37	10.308%	$142.7055	$142.71	$142.70	$142.70
Purchase #5	$152.73	7.729%	$164.5345	$164.53	$164.55	$164.50
Purchase #6	$220.64	8.253%	$238.8494	$238.85	$238.85	$238.80
Purchase #7	$56.82	5.721%	$60.0707	$60.07	$60.05	$60.10
7 purchase totals =	$1,042.32		$1,126.0651	$1,126.06	$1,126.05	$1,126.00